Method for changing the operating mode of an internal combustion engine

Abstract

In a method for changing the operating mode in an internal combustion engine it is possible to switch between an operating mode with spark ignition of the engine and an operating mode with auto-ignition of the engine. Hereby, a first map is provided in which at least one range is specified in which a suitable auto-ignition of the engine can take place. After the engine start, therefore, it is determined whether the engine has reached an operating point lying within this range of the first map in order then to switch the engine to the operating mode in which auto-ignition can take place reliably.

1. An internal combustion engine which can be switched at least between an operating mode with spark ignition of the engine and an operating mode with controlled auto-ignition of the engine, the internal combustion engine being operable:
 to provide a first map in which at least one range is specified in which auto-ignition of the engine can take place, 
 to determine whether, after an engine start, the engine reaches an operating point lying in the range of the first map, in which a controlled auto-ignition can take place, and 
 to switch the engine to the operating mode, in which the auto-ignition can take place when the operating point lies in this range of the first map. 
 
     
     
       2. A method for changing the operating mode of an internal combustion engine from an operating mode in which a spark ignition of the engine takes place into an operating mode in which auto-ignition of the engine takes place, the method comprising the steps of:
 a) providing a first map in which at least one range is specified in which auto-ignition of the engine can take place, 
 b) determining whether, after an engine start, the engine reaches an operating point lying in the range of the first map, in which a controlled auto-ignition can take place, and 
 c) switching the engine to the operating mode, in which the auto-ignition can take place when the operating point lies in this range of the first map. 
 
     
     
       3. The method according to  claim 2 , wherein a reference map is provided for at least one reference fuel with a data supply from operating ranges of at least one or substantially all operating modes in order to draw conclusions regarding the fuel quality of the fuel in the tank. 
     
     
       4. The method according to  claim 2 , wherein a pressure curve analysis is performed after the engine has switched to the operating mode in that auto-ignition of the engine can take place. 
     
     
       5. The method according to  claim 2 , wherein in the first combustion or in several of the first combustions after the switchover into the operating mode in which auto-ignition of the engine can take place, one or more parameters selected from the group consisting of the pressure course, the pressure gradient, the ignition point, the acoustic behavior, the combustion duration and the emissions are determined in order to draw conclusions therefrom regarding the fuel quality or fuel properties. 
     
     
       6. The method according to  claim 2 , wherein the fuel quality and/or fuel composition is determined online for the adjustment of operating parameters of operating points during driving and stored in corresponding maps in the engine control system so that a corresponding operating range for a existing fuel can be created. 
     
     
       7. The method according to  claim 2 , wherein the operating mode in which auto-ignition can take place is, for example, a CAI operating mode. 
     
     
       8. The method according to  claim 2 , wherein a reference map is provided for at least one reference fuel with substantially a complete data supply from operating ranges of at least one or substantially all operating modes in order to draw conclusions regarding the fuel quality of the fuel in the tank. 
     
     
       9. The method according to  claim 2 , wherein in the first map, the range for the operating mode in which auto-ignition of the engine can take place is selected in such a way that an operating point of the engine in this range ensures sufficient switchover reliability and optionally comprises a stable engine operation for a predetermined fuel quality range. 
     
     
       10. The method according to  claim 9 , wherein, after refueling a vehicle, the fuel quality of the fuel in the tank is determined in dependence on the quantity and quality of the newly filled fuel and any residual fuel in the tank. 
     
     
       11. The method according to  claim 2 , wherein a switchover into the operating mode in which auto-ignition of the engine can take place, takes place under the aspect of the driving comfort. 
     
     
       12. The method according to  claim 11 , wherein the switchover into the operating mode is virtually or substantially completely imperceptible to a driver. 
     
     
       13. The method according to  claim 2 , wherein a coarse adjustment of at least one or more operating parameters takes place when an operating point of the engine falls within the range of the first map in which a controlled auto-ignition of the engine can take place. 
     
     
       14. The method according to  claim 13 , wherein the coarse adjustment of the operating parameters takes place on one or more parameters selected from the group consisting of:
 the antiknock properties of the fuel, the volatility of the fuel, the fuel quality in the tank after a refueling process, the idle time of the vehicle, the ambient temperature, the time since the last switchover process, and the range for operating points in which a controlled auto-ignition is possible. 
 
     
     
       15. The method according to  claim 13 , wherein as operating parameters in the coarse adjustment and/or the fine adjustment one or more operating parameters can be adjusted, wherein the one or more operating parameters are selected from the group consisting of: the adjustment of the injection timing and the injection quantity, the lambda variation, the adjustment of the exhaust gas recirculation rate, the adjustment of the prehomogenization in the intermediate compression, the adjustment of the ignition point, the ignition support by at least one or more spark plugs during the auto-ignition, the intake-air preheating and intake-air precooling, and the adjustment of the control times of variable valve gears and the control of air pulse valves. 
     
     
       16. The method according to  claim 13 , wherein the operating parameters are derived from the operating mode with spark ignition. 
     
     
       17. The method according to  claim 2 , wherein a fine adjustment of at least one or more operating parameters takes place after the engine has switched to the operating mode in that auto-ignition of the engine can take place. 
     
     
       18. The method according to  claim 17 , wherein during the fine adjustment of at least one or more operating parameters selected from the group consisting of: the idle time of the vehicle, the ambient temperature and the time since the last switchover process are taken into account. 
     
     
       19. The method according to  claim 17 , wherein a current operating point at which a fine adjustment of at least one operating parameter has taken place and at which auto-ignition of the engine can take place is validated and stored in a second map. 
     
     
       20. The method according to  claim 19 , wherein a changeover to the operating mode in which auto-ignition of the engine can take place can only take place in a validated operating point or an operating point which falls in a pre-specified range in which auto-ignition of the engine can take place.